Retrofit decentralised ventilation in an older home – no ducts, with heat recovery

Giving an older home an energy-efficient refurbishment makes it airtight – and that is exactly where the trouble often begins. New windows, insulated façades and sealed joints keep the heat inside the house, but they trap the moisture just as effectively. The good news: a decentralised home ventilation system with heat recovery can be retrofitted in an older building – with no elaborate ductwork, no suspended ceilings and usually in just a few hours per room. In this guide you will learn how it works, what to look out for and which model suits which room.

🏠 Why an airtight refurbishment needs fresh air

An unrenovated older house “breathes” through leaky windows and joints – uncontrolled, draughty and expensive. After the refurbishment, that natural air exchange is gone. Moisture from showering, cooking, laundry and breathing stays in the rooms and condenses on the coldest surfaces. The result is fogged-up windows, stuffy air and, in the worst case, mould.

That is why a ventilation assessment is required for refurbishments (in Germany under DIN 1946-6, in England under Approved Document F): it checks whether the planned ventilation is sufficient to remove moisture reliably. A decentralised ventilation system delivers a controlled, continuous air exchange here – while at the same time reducing the burden of moisture, mould and even radon.

🔄 Retrofitting without ducts: how the principle works

The big advantage of decentralised units: they need no branched pipe system running through the entire house. Each unit is fitted directly into the exterior wall of the room it serves and works on its own.

Inside sits a ceramic heat accumulator. The unit reverses its direction in a steady cycle: first the fan carries the warm, stale indoor air outside – and the ceramic core absorbs its heat. Then the direction switches, and the incoming fresh outdoor air is reheated by that stored warmth as it flows in. This keeps up to 93% of the heat inside the house instead of letting it escape unused. And it does so whisper-quietly: Ambientika units operate from as little as 20 dB.

🔧 The installation step by step

Retrofitting is surprisingly straightforward and essentially comes down to drilling a single core hole through the exterior wall:

• → Choose the location: Ideally on an exterior wall, preferably opposite doors for good cross-ventilation.
• → Drill the core hole: A suitable bore through the exterior wall creates space for the wall sleeve – angled slightly outwards so that no water can get in.
• → Insert the wall sleeve: It houses the technology and provides a clean finish.
• → Mount the unit: The heat exchanger and fan are slid into place, with the weather hood on the outside and the design cover on the inside.
• → Connect the power: Decentralised units only need a simple electrical connection.

Because no ductwork is laid, mess stays minimal and the effort per room remains manageable. For many people renovating, this is the decisive reason to go for the decentralised option.

✅ What to watch out for when retrofitting

• ✓ Paired operation for heat recovery: For a balanced air exchange, the units work best in pairs, alternating their cycle.
• ✓ Treat wet rooms separately: Bathrooms and WCs need a solution with targeted moisture extraction.
• ✓ Sound insulation on noisy façades: Thanks to values from 20 dB, it stays quiet even at night.
• ✓ Keep maintenance in mind: The filter change is tool-free – no specialist required, done in a few simple steps.
• ✓ Ventilation concept to DIN 1946-6: Have your requirement calculated professionally before you order any units.

A plus for peace of mind: every unit is certified by IFT Rosenheim and TÜV – developed and manufactured by Südwind GmbH, a South Tyrolean family business with over 60 years of experience.

🧩 Which model suits which room?

A single room: For an individual bedroom, child’s room or study, the Ambientika solo+ is the ideal way to start (from 379 €).

Coupling several rooms: The wired Ambientika advanced+ (519 €) can be linked with up to 15 units and offers free cooling. Where no cables should be laid, the wireless Ambientika wireless+ (579 €) is the elegant alternative. For smart-home control there is the smart (619 €), and for commercial spaces the Office (699 €).

Bathroom and wet rooms: The Ambientika advanced B+ (439 €) is designed specifically as a bathroom fan and responds automatically via a humidity sensor.

You will find an overview in our product overview.

💶 Making the most of refurbishment funding

Ambientika units are eligible for government funding programmes (for example KfW and BAFA in Germany). Ventilation systems with heat recovery count as an efficiency measure and can form part of a subsidised refurbishment project. Because funding schemes and terms change, it is best to have the specific options checked as part of your individual ventilation concept.